It would be worth trying to figure out whether there is a correctable humidity problem going on. That is a *gorgeous* coop, but it is still a considerable number of birds in there and it would probably be worth buying a hygrometer, calibrating it (that is, using the salt method to calculate its personal correction factor, see the 'Incubating And Hatching Eggs' section of BYC for directions), and then leaving it out there for a few days to find out what your nighttime humidity is.
If humidity readings (corrected for the hygrometer's inaccuracy) are below 60-70%, then I'd say you probably just have unusually susceptable roos; OTOH if they are higher, and I could certainly imagine they might be, then it would be worth seeing whether some structural or management changes might help. (Ventilation won't cure severely damp *weather* but usually when it's that cold it isn't that humid in the coop, so IMO most often it's a management issue not a climate issue).
Good luck, have fun,
Pat
If humidity readings (corrected for the hygrometer's inaccuracy) are below 60-70%, then I'd say you probably just have unusually susceptable roos; OTOH if they are higher, and I could certainly imagine they might be, then it would be worth seeing whether some structural or management changes might help. (Ventilation won't cure severely damp *weather* but usually when it's that cold it isn't that humid in the coop, so IMO most often it's a management issue not a climate issue).
Good luck, have fun,
Pat